Processing of flexible substrates, such as plastic films or foils, is in high demand in the packaging industry, semiconductor industries and other industries. Processing may consist of coating of a flexible substrate with a desired material, such as a metal, in particular aluminum. Systems performing this task generally include a processing drum, e.g., a cylindrical roller, coupled to a processing system for transporting the substrate and on which at least a portion of the substrate is processed. Roll-to-roll coating systems can, thereby, provide a high throughput system, e.g. for the packaging industry. For example, transparent layers as barriers for oxygen or water vapor can be deposited.
Typically, an evaporation process, such as a thermal evaporation process, can be utilized for depositing thin layers of metals, which can be metallized onto flexible substrates, such as plastic or pre-coated paper. However, evaporation processes can also be used in other deposition apparatus for non-flexible substrates, such as glass substrates, metal substrates, wafers, or the like.
Metal oxide layers can, for example, be evaporated with the reactive evaporation process. Thereby, the metal is evaporated and the reactive gas, such as oxygen, is provided in the vapor of the metal. This evaporation method can, for example, be used for depositing aluminum oxide, aluminum nitride, aluminum oxynitride, and corresponding materials of other materials on substrates. Thereby, oxygen or the like is preferably provided directly in the vapor of aluminum. In light of the fact that aluminum vapor is highly reactive and aggressive and in light of the fact that the reactive gas needs to be guided close to the aluminum vapor or even within the cloud of aluminum vapor, there is a plurality of difficulties. Even though these difficulties might be particularly crucial for reactively depositing aluminum oxide, similar difficulties might occur for other deposition processes where metals or other materials are reactively deposited as oxides, nitrites or other forms. Typical further materials can be Bi, Zn, Sn, In and Ag.
In view of the above, it is an object to provide an improved gas lance unit, an improved evaporation apparatus and an improved evaporation process to overcome at least some of the problems in the art.